In the 1970s, sawmill workers could talk about technical matters or insult each other in their own special sign language.

When the linguists Martin Meissner and Stuart Philpott first started visiting sawmills in British Columbia in the 1970s, they thought they’d find workers communicating without speaking, probably with some simple gestures that contained technical information. There was a long history of such communication in the face of extreme noise: For centuries, American mill workers had used systems of hand signals to tell each other, across the unending roar of the saws, how to cut wood.

What they discovered, though, floored them. The researchers witnessed a sign language system complete enough that workers could call each other “you crazy old farmer,” tell a colleague that he was “full of crap,” or tell each other when the foreman was “fucking around over there.”

Outside of deaf communities, hearing people sometimes develop what are now often called “alternate sign languages” to communicate when words will not do. In monasteries, monks uses signs to communicate in areas where speech is forbidden, for instance. In industries where machines made speaking impossible—in ships’ engine rooms, in steel mills, textile mills, and sawmills—workers also found ways to communicate with their hands.

In 1955, when Popular Mechanics covered these industrial sign languages, many were already disappearing. But in the 1970s, Meissner and Philpott found a sign language still used in sawmills. Their research further honed in on the culture of one particular mill where workers had developed a system of 157 signs that they used not just to communicate about their work but to trade small talk, tell crude jokes and tease each other.

The linguist were struck by the language’s “ingenuity and elegance,” they wrote. It was also a secret hidden in plain sight: the mill workers’ bosses, it seems, had almost no idea what they were saying.

The core of the sawmill workers’ sign language was a system of numbers, standardized across the industry. Those signs were shared in a technical notebook, and, the linguists wrote,”in the view of the management, that was about all there was to the language.” But it covered much more ground than technical communication. Workers could talk about quitting time, lunch time, and cigarette breaks. They could talk about sports and the bets they placed on games. They could talk about their wives, cars, and colleagues. They could tell jokes and comment on what was going on around them without their bosses ever knowing.

In one conversation that Meissner and Philpott recorded, one worker pointed out the boss, by signing “Big shot there,” and noted that he was with three women. The worker also commented that one of the women had a great figure and “then drew a rectangle with his index finger and pointed to the head sawyer’s operating cubicle, wanting to liken the woman he described to the calendar nude behind the sawyer,” the researchers wrote. “She’s my girlfriend,” he told the others.

Some of the signs were transparent enough. To ask "What time is it?" or "How long?" a worker would tap his wrist (sign 126 below). Others had straight-forward associations: the sign for "woman" (128 below) was an up-and-down movement "suggesting a woman's breast," the researchers wrote. Some would have been much harder to guess, though: clutching a bicep was the sign for both "weak" and "week" (125 below).

There were some social rules governing how these signs were used. All the workers learned the technical signs, but the whole corpus of the language took about six months to master and not everyone managed it. The conversational signs were more likely to be used by people who’d worked together for a few years and had similar status, education and ethnic background. It was also more popular with men who didn’t mind everyone knowing what they had to say.

Compared to a fully developed sign language, which can have thousands of signs, this one was limited in its scope. It did provide these men with a way to cover the basic grounds of collegial small talk, and in at least one case, sawmill sign language also worked in the home. A couple of years after Meissner and Philpott published their research on British Columbia’s mills, another linguist, Robert Johnson, found a retired sawmill worker in Oregon who had lost his hearing and used a variant on sawmill sign language to communicate with his wife and son, who was also deaf. About three-quarters of their corpus of 250 signs overlapped with the British Columbia sawmill signs Meissner and Philpott had collected. There was also significant overlap with American Sign Language.

The family used their particular sign language to communicate about the grist of daily life; they had signs for quiet, mirror, eat, shave, stink, happy, deer, fish, church, baby and so on. They never learned ASL because no one around them used it and their system of signs worked well enough. There were shortcomings, though.

“When it comes to feelings, you have real problems,” the wife told the Eugene Register-Guard. “You can say you’re angry...But other feelings are so subtle and complex….” Her solution: just write them down.

When visiting sawmills and other industrial settings, Meissner and Philpott noticed another trend. Where there was more automation, hand signals were less likely to be used. They predicted that as automation in factories increased, the use of sign language would decrease. In other, less noisy industries, radios and walkie-talkies already were limiting the need for hand signals, previously an advantage over shouting. Today, it’s rare, if not impossible to find reports of site-specific sign languages being used in factories.